The quinacridonequinones are known to form solid solutions with quinacridones. These solid solutions are maroon-colored pigments with good weathering fastness properties. However, due to the blueish-red color of the quinacridone component, it is not possible to retain the intense yellow color of the quinacridonequinone component.
The use of solid solutions containing quinacridonequinone and anilinoacridones as a pigment has been described in U.S. Pat. No. 4,286,998.
Binary solid solutions containing a quinacridone and/or quinacridonequinone component and a pyrrolo[3,4-c]pyrrole component, without an anilinoacridone or phenoxyacridone component, are described in U.S. Pat. No. 4,810,304. This publication provides a general suggestion that the addition of light-stabilizers, including anilinoacridones, before, during or after formation of the solid solution, may improve the lightfastness of the disclosed solid solutions. The publication does not suggest that the anilinoacridone could or should be incorporated into the crystal lattice of the solid solution to form a ternary solid solution.
The present invention relates to ternary solid solutions containing a quinacridonequinone component, a pyrrolo[3,4-c]pyrrole component and a third component which is a 2-anilinoacridone, a 5,6,7,8-tetrahydro-2-anilinoacridone, a 2-phenoxyacridone, a 5,6,7,8-tetrahydro-2-phenoxyacridone or a mixture thereof. The present ternary solid solutions show a great degree of improvement in lightfastness over binary solid solutions containing only the quinacridonequinone component and the pyrrolo[3,4-c]pyrrole component, and yet show the full range of attractive shades that the binary solid solutions display.
Another aspect of this invention relates to quaternary solid solutions containing the quinacridonequinone component, the pyrrolo[3,4-c]pyrrole component, the third acridone component and a quinacridone component. These quaternary solid solutions are attractive maroon pigments with excellent saturation, color strength and durability properties.
It is necessary to incorporate the photostabilizing acridone component into the solid solution in order to acheive the superior photostability found in both the ternary and quaternary solid solutions of the present invention. Thus, the present solid solutions demonstrate surprisingly superior photostability when compared to a physical mixture containing the acridone component and a preformed solid solution of only the quinacridonequinone component and the pyrrolo[3,4-c]pyrrole component.